TITLE: GCN CIRCULAR NUMBER: 20303 SUBJECT: IPN Triangulation of GRB 161218B (long/very bright) DATE: 16/12/20 09:25:37 GMT FROM: Dmitry Svinkin at Ioffe Institute D. Svinkin, S. Golenetskii, R. Aptekar, D. Frederiks, A. Kozlova, and T. Cline on behalf of the Konus-Wind team, K. Hurley, on behalf of the IPN, S. Barthelmy, J. Cummings, N. Gehrels, H. Krimm, and D. Palmer, on behalf of the Swift-BAT team, A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo, and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team, and V. Connaughton, M. S. Briggs, C. Meegan, V. Pelassa, and A. Goldstein, on behalf of the Fermi GBM team, report: The long-duration, very bright GRB 161218B has been detected by Fermi (GBM; Hamburg et al., GCN Circ. 20286), Konus-Wind, INTEGRAL (SPI-ACS), Swift (BAT), and POLAR (Wang et al., GCN Circ. 20288), so far, at about 30760 s UT (08:32:40). The burst was outside the coded field of view of the BAT. We have triangulated it to a preliminary, 3 sigma error box whose coordinates are: --------------------------------------------- RA(2000), deg Dec(2000), deg --------------------------------------------- Center: 0.888 (00h 03m 33s) -14.700 (-14d 42' 00") Corners: 2.344 (00h 09m 23s) -18.473 (-18d 28' 23") 3.138 (00h 12m 33s) -17.987 (-17d 59' 13") 359.466 (23h 57m 52s) -10.927 (-10d 55' 37") 358.690 (23h 54m 46s) -11.401 (-11d 24' 03") --------------------------------------------- The error box area is 7.05 sq. deg, and its maximum dimension is 8.0 deg (the minimum one is 53.5 arcmin). The Sun distance was 87 deg. This box may be improved. A triangulation map is posted at http://www.ioffe.ru/LEA/GRBs/GRB161218_T30761/IPN The Konus-Wind time history and spectrum will be given in a forthcoming GCN Circular.